how do you pick the hour, minute and second from the posixct formated datetime in R

Question

I have a data frame like this:

dput(tail(x,10))
structure(list(DATE = structure(c(1375725600, 1375729200, 1375732800, 
1375736400, 1375740000, 1375743600, 137574         


        

Answer 1

this worked:

x$t<-strftime(x$DATE, format="%H:%M:%S")

Answer 2

You can use lubridate to get the components in hours, minutes and seconds of your dates:

library(lubridate)
transform(x,time.str = format(DATE,'%H:%M:%S'),
              hour = hour(DATE),
              minute = minute(DATE),
              second= second(DATE))

                    DATE  VOLUME    PC time.str hour minute second
3399 2013-08-05 20:00:00 2790797 10.12 20:00:00   20      0      0
3400 2013-08-05 21:00:00 2670868  9.95 21:00:00   21      0      0
3401 2013-08-05 22:00:00 2586397  9.90 22:00:00   22      0      0
3402 2013-08-05 23:00:00 2470043  9.46 23:00:00   23      0      0
3403 2013-08-06 00:00:00 2336334  8.99 00:00:00    0      0      0
3404 2013-08-06 01:00:00 2228206  8.94 01:00:00    1      0      0
3405 2013-08-06 02:00:00 2129270  9.79 02:00:00    2      0      0
3406 2013-08-06 03:00:00 2032518  8.45 03:00:00    3      0      0
3407 2013-08-06 04:00:00  872133  8.85 04:00:00    4      0      0
3408 2013-08-06 05:00:00  725377  8.50 05:00:00    5      0      0